Download Chapter 11 - Principles of Disease and Epidemiology

Chapter 11 - Principles of Disease and
Epidemiology
• Pathology
Study of disease
• Etiology
Study of the cause of a disease
• Pathogenesis
Development of disease
• Infection
Colonization of the body by
pathogens
• Disease
An abnormal state in which the
body is not functioning normally
Normal Microbiota and the Host
• Transient microbiota may be present for days, weeks,
or months
• Normal microbiota permanently colonize the host
• Symbiosis is the relationship between normal
microbiota and the host
Normal Microbiota and the Host:
• In
one organism is benefited
and the other is unaffected.
• In
both organisms benefit.
• i.e. E. coli produces vitamin K (and some B)
• In parasitism, one organism is benefited at the
expense of the other.
Normal Microbiota and the Host:
• Locations of normal
microbiota on and in
the human body
Figure 14.2
Normal Microbiota and the Host:
• Microbial antagonism is competition between
microbes.
• Normal microbiota protect the host by:
• occupying niches that pathogens might occupy
• producing acids
• producing bacteriocins
Normal Microbiota and the Host:
• Some normal microbiota are opportunistic pathogens.
•
(vaginal yeast infection)
• Normal location: vagina, mouth
•
(urinary tract infections)
• Normal location: large intestine
Normal Microbiota and the Host:
•
(hospital acquired
diarrhea; may cause pseudomembranous colitis)
• Normal location: large intestine
•
(a major cause
of meningitis)
• Normal location: nasopharynx
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•
are live microbes applied to or ingested
into the body, intended to exert a beneficial effect.
•
are chemicals used to promote growth
of beneficial microbiota
Classifying Infectious Diseases
• Symptom
A change in body function that is
felt by a patient as a result of
disease
• Sign
A change in body function that
can be measured or observed as a
result of disease.
• Syndrome
A specific group of signs and
symptoms that accompany a
disease.
Classifying Infectious Diseases
• Communicable disease
A disease that can be
spread from one host to
another.
• Contagious disease
A disease that is easily
spread from one host to
another.
• Noncommunicable disease A disease that is not
transmitted from one host
to another.
• i.e. Chicken pox, measles, common cold are contagious
• i.e. Tetanus, Anthrax are noncommunicable
Occurrence of Disease
• Incidence
Number of new cases of a disease
during a specific time period.
• Prevalence
Total number of old and new cases
of a disease during a specific time
period.
• Sporadic disease
Disease that occurs
occasionally in a population.
• i.e. Eastern Equine Encephalitis
Occurrence of Disease
•
Disease constantly present in a
population. i.e. common cold
• Epidemic disease
Disease acquired by many
hosts in a given area in a short
time. i.e. influenza,
• Pandemic disease
Worldwide epidemic.
i.e. influenza; AIDS
•
Immunity in most of a population.
Severity or Duration of a Disease
• Acute disease
Symptoms develop rapidly, but
last a short time. i.e. influenza,
cold
• Chronic disease
Disease develops slowly, lasts a
long time. i.e.
Hepatitis B
• Subacute disease
Symptoms between acute and
chronic. i.e. gingivitis
• Latent disease
Disease with a period of no
symptoms when the “microbe” is
inactive. i.e. genital herpes,
Extent of Host Involvement
• Local infection
Pathogens limited to a specific
area of the body. i.e. pulmonary
Tuberculosis; Strep throat
• Systemic infection
An infection throughout the body.
• Focal infection
Systemic infection that began as
a local infection.
i.e. Tuberculosis; Tetanus
• Bacteremia
Bacteria in the blood
• Septicemia
Growth of bacteria in the blood
Extent of Host Involvement
• Toxemia
Toxins in the blood
• Viremia
Viruses in the blood
• Primary infection
Infection that causes the
initial illness; often acute
•
• Secondary infection
Opportunistic infection after a
primary (predisposing) infection
The Stages of a Disease
Figure 14.5
Reservoirs of Infection
• Reservoirs of infection are the primary receptacles of the
infectious agent. They may or may not be the direct
source of the infection.
• Animal
•
dogs, bats, racoons, foxes,
other mammals
• Rocky Mountain Spotted Fever: ticks
•
soil, infected cows, sheep,
other animals
•
may be transmitted to humans
Reservoirs of Infection
• Human — HIV, gonorrhea
• Carriers may have inapparent infections or latent
diseases
• Nonliving —
• Soil: Botulism (Clostridium botulinum), Tetanus
(Clostridium tetani)
• Water: Cholera (Vibrio cholerae)
• Food: Tapeworm
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Transmission of Disease
• Contact
• Direct
Requires physical contact between
infected and susceptible host
• Indirect
Spread by
• Droplet
Transmission via airborne droplets;
usually travel less than one meter
TORTORA • FUNKE
• CASE
Microbiology
AN INTRODUCTION
EIGHTH EDITION
B.E Pruitt & Jane J. Stein
PowerPoint® Lecture Slide Presentation prepared by Christine L. Case
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Transmission of Disease
• Vehicle
Transmission by an inanimate reservoir
(food, water, air)
• Vectors
Insects, especially fleas, ticks, and
mosquitoes
•
Insect carries pathogen on feet.
•
Pathogen reproduces in vector.
i.e. Malaria, Rocky Mountain
Fever disease
Spotted
TORTORA • FUNKE
• CASE
Microbiology
AN INTRODUCTION
EIGHTH EDITION
B.E Pruitt & Jane J. Stein
PowerPoint® Lecture Slide Presentation prepared by Christine L. Case
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Nosocomial (Hospital-Acquired) Infections
• Are acquired as a result of a hospital stay
• 5-15% of all hospital patients acquire nosocomial
infections
• A leading cause of death in U.S.
Figure 14.7, 9
Relative frequency of nosocomial infections
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Common Causes of Nosocomial Infections
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Emerging Infectious Diseases
• Diseases that are new, increasing in incidence, or
showing a potential to increase in the near future.
• Contributing factors:
• Evolution of new strains
•
• Inappropriate use of antibiotics and pesticides
• Antibiotic/pesticide resistant strains
• Changes in weather patterns (and global warming?)
•
(and malaria)
Emerging Infectious Diseases
• Contributing factors:
• Modern transportation
•
• Ecological disaster, war, expanding human settlement
• Ebola
• Animal control measures
•
• Public Health failure
• Diphtheria
Epidemiology
• The study of where and
when diseases occur
• How they’re transmitted
• How many infected
Figure 14.11
Epidemiology
John Snow
1848-1849
Mapped the occurrence of
cholera in London
Ignaz Semmelweis
1846-1848
Showed that hand washing
decreased the incidence of
puerperal fever
Florence Nightingale
1858
Showed that improved
sanitation decreased the
incidence of epidemic typhus;
backed by statistics
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
• Descriptive
Collection and analysis of data
regarding occurrence of disease
Snow
• Analytical
Comparison of two different
diseased groups OR diseased and
healthy groups
Study of a disease using controlled
experiments
Nightingale
• Experimental
• Case reporting
• Nationally Notifiable
Diseases
Health care workers report specified
disease to local, state, and national
offices
Physicians are required to report
occurrence
Semmelweis
Table 14.7
TORTORA • FUNKE
• CASE
Microbiology
AN INTRODUCTION
EIGHTH EDITION
B.E Pruitt & Jane J. Stein
PowerPoint® Lecture Slide Presentation prepared by Christine L. Case
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Centers for Disease Control and Prevention (CDC)
• Collects and analyzes epidemiological information in the
U.S.
• Publishes Morbidity and Mortality Weekly Report
(MMWR) www.cdc.gov
• Morbidity: incidence of a disease
• Mortality: death from disease